DSM-G600, DNS-3xx and NSA-220 Hack Forum

Hi folks, I would require some advise to where to start my searches. I have two DNS-323:  1) at home, where my windows computers (wired & wireless) back-ups their data (with their own bkp-up software), 2) a remote DNS-323 at another location.

What I want is plane simple: 

A- I want 2) to be an exact mirror of 1). No incremental backups, no compressed zip/tar files, etc... I want to be able to log to 2) and browse to the files there as if it was a normal server. No saving different version of files in case I do a mistake, etc. Plane simple mirror, of the directory I tell 1) to backup (ie I don't want to transfer my movies for example, to save bandwith).

B- I want the transfers for daily backup (or mirror updating) to be very efficient, to save bandwith, as I don't have unlimited upload!

C- secure transfer of course !

Any thoughts? I've looked at rsync a little be but wonder if this is the right tool. I've also looked at other things like duplicity, rdiff, rsnapshot, etc.  but they seems old, and more to make incremental bkp-up and "Time machine"....

thanks